Humans are unable to synthesise L‐ascorbic acid (L‐AA, ascorbate, vitamin C), and are thus entirely dependent upon dietary sources to meet needs. In both plant and animal metabolism, the biological functions of L‐ascorbic acid are centred around the antioxidant properties of this molecule. Considerable evidence has been accruing in the last two decades of the importance of L‐AA in protecting not only the plant from oxidative stress, but also mammals from various chronic diseases that have their origins in oxidative stress. Evidence suggests that the plasma levels of L‐AA in large sections of the population are sub‐optimal for the health protective effects of this vitamin. Until quite recently, little focus has been given to improving the L‐AA content of plant foods, either in terms of the amounts present in commercial crop varieties, or in minimising losses prior to ingestion. Further, while L‐AA biosynthesis in animals was elucidated in the 1960s,1 it is only very recently that a distinct biosynthetic route for plants has been proposed.2 The characterisation of this new pathway will undoubtedly provide the necessary focus and impetus to enable fundamental questions on plant L‐AA metabolism to be resolved. This review focuses on the role of L‐AA in metabolism and the latest studies regarding its biosynthesis, tissue compartmentalisation, turnover and catabolism. These inter‐relationships are considered in relation to the potential to improve the L‐AA content of crops. Methodology for the reliable analysis of L‐AA in plant foods is briefly reviewed. The concentrations found in common food sources and the effects of processing, or storage prior to consumption are discussed. Finally the factors that determine the bioavailability of L‐AA and how it may be improved are considered, as well as the most important future research needs. © 2000 Society of Chemical Industry

BackgroundMetabolic syndrome (MetS) is a clustering of cardiovascular risk factors, which is associated with diabetes mellitus and cardiovascular disease. Lifestyle interventions applied to people with MetS has considerable beneficial effects on disease preventive outcomes. This study aimed to examine the effects of 1-year of yoga exercise on the cardiovascular risk factors including central obesity, hypertension, dyslipidemia and hyperglycemia in middle-aged and older Hong Kong Chinese adults with MetS.MethodsAdults diagnosed with MetS using National Cholesterol Education Program criteria (n = 182; mean ± SD age = 56 ± 9.1) were randomly assigned to a 1-year yoga intervention group or control group. Systolic and diastolic blood pressure, waist circumference, fasting plasma glucose, triglycerides, and high-density lipoprotein cholesterol were examined at baseline, midway, and on completion of the study. Physical activity level and caloric intake were assessed and included in the covariate analyses.ResultsA reduction of the number of diagnostic components for MetS was found to be associated with the yoga intervention. Waist circumference was significantly improved after the 1-year yoga intervention. A trend towards a decrease in systolic blood pressure was observed following yoga intervention.ConclusionThese results suggest that yoga exercise improves the cardiovascular risk factors including central obesity and blood pressure in middle-aged and older adults with MetS. These findings support the complementary beneficial role of yoga in managing MetS.

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Aim.  To review systematically the literature about barriers to diabetes self‐care from both patients’ and healthcare providers’ perspectives. Background.  Diabetes mellitus is a global health concern due to rapidly increasing prevalence. The healthcare costs for diabetes care and related complications are high. Tight glycaemic control achieved by intensive therapy has been shown to lower the risk of complications. Despite the provision of comprehensive management programmes, patients are often unable to achieve the desired outcomes. It is essential to understand the barriers to diabetes self‐care in order to promote successfully self‐care behaviours. Methods.  A search of OVID Medline (R), CINAHL, Cochrane Library and British Nursing Index was carried out during 1986–2007 using keywords: Type 2 Diabetes Mellitus, self care, patient compliance, patient adherence and barriers to diabetes self care. Manual searching of relevant nursing journals and sourcing of secondary research extended the search. Results.  A total of 16 original research papers using various methods including survey, descriptive correlational, sequential explanatory mixed‐method and qualitative exploratory design were reviewed. In total, over 8900 patients and 4550 healthcare providers were recruited from over 28 countries in these studies. Major barriers identified included psychosocial, socioeconomic, physical, environmental and cultural factors. Conclusions.  Healthcare providers can enhance patient empowerment and participation with family support to achieve feasible targets. Better health care delivery systems and reforms that improve affordability, accessibility, and efficiency of care are essential for helping both providers and patients to meet desirable standards of diabetes care. Relevance to clinical practice.  Understanding barriers to diabetes self‐care is the first step in facilitating providers to identify their role in enabling patients to overcome these barriers. Healthcare providers can develop strategies to clarify and individualise treatment guidelines, implement continuing education, improve communication skills, and help motivate patients to achieve desired behavioral changes.

Results of international correlation and migrant studies suggest that dietary fat promotes carcinogenesis in hormone-sensitive sites, but this is disputed. In the present study, we used a Noble rat model of sex hormone-induced cancers to examine the effect of a high-fat diet on the incidence and latency of prostate and mammary cancer in male (n 139) and female (n 72) animals respectively. We also measured a-tocopherol levels in female breast tissue to determine whether a high intake of polyunsaturated fatty acids depletes antioxidant defence in target tissues, providing a possible potentiating mechanism for carcinogenesis. Results showed a very high incidence of hormone-induced adenocarcinomas of prostate and mammary gland, irrespective of diet. There was no difference in the pattern of carcinogenesis in different prostatic locations, weight of the prostate, or weight gain between male rats on the high-fat diet compared with the control (standard, low-fat) diet. In female rats, the incidence of mammary cancer and the body-weight gain were the same in both dietary groups, and breast a-tocopherol was also unaffected by dietary fat intake. Our present results are supportive of recent cohort studies that reported no significant association between intake of fat and the development of human prostate and breast cancer, and do not support a role for dietary fat in promoting sex hormone-induced prostate and mammary carcinogenesis.Noble rats: Prostate cancer: Breast cancer: Carcinogenesis: Dietary fat: Vitamin E The global incidence of cancer is increasing both absolutely and in relation to other diseases, and the incidence is projected to rise from 10·3 million cases in 1996 to